1. Field of the Invention
The present invention relates to the production of melts from raw materials including refractory materials and glass-based materials. In addition, the present invention relates to an apparatus for the heat treatment of raw materials for the production of a melt and methods of forming a melt that is chemically and physically homogeneous.
2. Discussion of Related Art
In the discussion of the related art that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention, if appropriate.
Glassy fiber, which is currently produced from natural materials, such as basalt, can be made using a variety of methods. For example, continuous basalt fiber can be produced from melts formed in furnaces heated by gas burners or electrical heating elements. However, the heat distribution, changes in the composition of the melt (for example, by oxidation of divalent iron), imperfect homogenization of the melt, and the long period of time (approximately ten hours) the melt remains in the furnace, because, for example, the low thermal conductivity of silicate materials, can effect the melt. Such processes can result in a disproportionate consumption of energy, can use equipment incorporating precious metals, and can have limited equipment service life, thereby reducing the overall economic efficiency.
In another example, materials can be processed in a microwave furnace as disclosed in International Publication No. WO 00/78684 A1 published Dec. 28, 2000 and Czech patent application no. PV 2000-935 of 25 May 2000, the entire contents of both applications are herein incorporated by reference. The disclosed microwave process uses additives of a carbide, nitride, or boride group to activate the raw material for the absorption of microwave radiation. The disclosed microwave process is a single-stage process and is, thus, difficult to operate in a continuous fashion. Also, the single-stage furnace can impact the homogenization process and can reduce the quality of the formed melt, since the physical properties, such as viscosity, can be effected during charging of raw material into the melt. In addition, the single-stage method can complicate industrial application, since large-capacity production of melt is limited.
Additional examples of microwave furnaces and their applications are disclosed in WO 01/81258 A1, WO 01/96250 A1. U.S. Patent Application Publication No US 2002/0069678 A1, and U.S. Pat. No. 4,880,578 (Holcombe et al.), U.S. Pat. No. 4,940,865 (Johnson et al.), U.S. Pat. No. 4,957,434 (Radomsky), U.S. Pat. No. 5,254,818 (Aubert), U.S. Pat. No. 5,597,504 (Berson et al.) U.S. Pat. No. 5,822,879 (Vincent et al.), U.S. Pat. No. 5,869,816 (Strack et al.), U.S. Pat. No. 5,968,400 (Wicks et al.), and U.S. Pat. No. 6,262,405 B1 (Wicks et al.), the entire contents of each are herein incorporated by reference.